He said many hospital and clinics in Gauteng operated normally on Wednesday morning, at the start of the national strike in the public sector, but that disruptions occurred in the afternoon as employees joined protests.

"The union has promised a full-blown strike from tomorrow and the department has put in place contingency measures to mitigate against the strike," said Mahlangu.

These measures included the deployment of administrative staff from central and regional offices to assist the worst-affected clinics and hospitals.

Volunteers would be mobilised and hospital managers and senior officials on training would be called back. "All hospitals and clinics will remain open during the strike and the department will closely monitor the impact of the industrial action.

"All hospitals have established a strike committee, which will evaluate the situation regularly and call for assistance when necessary," Mahlangu said.

The 200 000-strong Public Servants' Association (PSA) will join the strike on Thursday.

On Wednesday members of Congress of SA Trade Unions-affiliated unions, including the SA Democratic Teacher's Union and the National Health and Allied Workers' Union, and the Independent Labour Caucus went on strike.